1. Field of the Invention
The invention relates to a wafer holding member such as an electrostatic chuck in an apparatus for manufacturing semiconductors wafer and glass substrate for liquid crystal display. The wafer holding member is to be used for fixing a wafer W such as a semiconductor wafer and glass substrate for liquid crystal display.
2. Description of the Related Art
In a process of manufacturing semiconductors, to carry out film formation or etching treatment for a wafer W such as a silicon wafer at a high precision, it is required to hold the wafer W while keeping the flatness of the wafer W. Conventionally, as holding means for that, mechanical type, vacuum chuck type, or electrostatic chuck type wafer holding members have been proposed.
Among these holding means, an electrostatic chuck type wafer holding member for holding a wafer W by electrostatic force is capable of easily satisfying the requirement to keep the flatness of a wafer W needed for various kinds of treatments such as film formation and etching. Particularly, with respect to the electrostatic chuck, it is possible to use the chuck in vacuum and corrosive gas atmosphere. Therefore, an electrostatic chuck type wafer holding member has been used widely in film formation apparatuses and etching apparatuses.
Along with the advancement of the integration degree of semiconductor devices, it is strongly needed to stabilize the properties of semiconductor devices, improve the yield, and increase of the number of wafers to be treated per unit time. Therefore, it is required to heat a wafer W to an aimed temperature as quick as possible and heighten a capability of uniformly heating the entire surface of the wafer W at the time of etching or film formation.
Therefore, it has been tried to improve the heat transfer property between a wafer W and an electrostatic chuck and to keep the surface temperature of the wafer W uniformly. To improve the heat transfer property between the wafer W and the electrostatic chuck, gas supply holes for introducing an inert gas such as He and Ar and grooves or recessed parts communicated with the gas supply holes are formed in a setting face to put the wafer W on. In the case the wafer W is attached to the setting face, the spaces formed between the wafer W and the grooves or the wafer W and the recessed parts are filled with an inert gas through the gas supply holes.
Japanese Patent No. 2,626,618 (Patent Document No. 1), Japanese Patent Laid-Open Nos. 6-112302 (Patent Document No. 2) and 2-119131 (Patent Document No. 3) describe the groove shapes and the recessed shapes to be formed on the setting faces. As shown in FIG. 6, these documents disclose an electrostatic chuck 31 which is provided with a gas supply hole 34 and a plurality of radial grooves 35 communicated with the gas supply hole 34 and circular grooves 36 communicated with the respective radial grooves 35 and arranged concentrically at approximately equal intervals around the above-mentioned gas supply hole 34 on the top face of the electrostatic chuck 31 and of which the top face except the radial grooves 35, the circular grooves 36 and the gas supply hole 34 for introducing a helium gas at 13 to 133 Pa into is used as the setting face 33 for a wafer W.
Also, Japanese Patent Laid-Open No. 10-56054 (Patent Document No. 4) discloses an electrostatic chuck, as shown in FIG. 7, which is provided with a gas supply hole 44 and a plurality of radial grooves 45 communicated with the gas supply hole 44 and a single circular groove 46 communicated with the end parts of the respective radial grooves 45 on the top face of the electrostatic chuck 31; of which the top face except the radial grooves 45, the circular groove 46 and the gas supply hole 44 is used as the setting face 43 for a wafer W; and in which the setting face 43 is blast-treated to form a roughened face in the setting face 43.
As shown in FIG. 8, Japanese Patent Laid-Open Nos. 7-153825 (Patent Document No. 5), 9-213777 (Patent Document No. 6), 7-18438 (Patent Document No. 7), and 8-55905 (Patent Document No. 8) disclose an electrostatic chuck 51 which is provided with a plurality of very small projected parts 52 dotted on the disk-like top face and a circular projected part 57 in the circumferential rim of the top face; in which the top faces of the very small projected parts 52 and the circular projected part 57 are used as the setting face 53 of the wafer W; and in which a plurality of gas supply holes 54 are formed in the top face to introduce helium gas at 13 to 1333 Pa into.
Further, Japanese Patent Laid-Open No. 2002-261157 (Patent Document No. 9) discloses an electrostatic chuck which is provided with a circular projected part formed in the circumferential rim part to put a wafer W thereon and a concave face formed in the center part.